Background-Driving is a complex form of activity involving especially cognitive and psychomotor functions. These functions may be impaired by Parkinson's disease. The relation between Parkinson's disease and driving ability is still obscure and clinicians have to make decisions concerning the driving ability of their patients based on insuYcent information. Until now no studies have compared diVerent methods for evaluating the driving ability of patients with Parkinson's disease. Methods-The driving ability of 20 patients with idiopathic Parkinson's disease and 20 age and sex matched healthy control subjects was evaluated by a neurologist, psychologist, vocational rehabilitation counsellor, and driving instructor using a standard 10 point scale. The patients and controls also evaluated their own driving ability. Cognitive and psychomotor laboratory tests and a structured on road driving test were used for evaluating the subjects' driving ability. Results-The patients with Parkinson's disease performed worse than the controls both in the laboratory tests and in the driving test. There was a high correlation between the laboratory tests and driving test both in the patient group and in the control group. Disease indices were not associated with the driving test. The neurologist overestimated the ability of patients with Parkinson's disease to drive compared with the driving ability evaluated by the structured on road driving test and with the driving related laboratory tests. Patients themselves were not capable of evaluating their own ability reliably. Conclusion-Driving ability is greatly decreased in patients with even mild to moderate Parkinson's disease. The evaluation of patients' driving ability is very diYcult to carry out without psychological and psychomotor tests and/or a driving test. (J Neurol Neurosurg Psychiatry 1998;64:325-330)

Stroke patients form a risk group as drivers due to their decreased cognitive and psychomotor abilities, and driving ability should always be evaluated after stroke. The results suggest that multidisciplinary neurological teams are able to evaluate the driving ability of stroke patients reliably. A careful evaluation of driving ability without a driving test requires assessment of cognitive and psychomotor functions critical in driving, which is not feasible for physicians without the support of a multidisciplinary team and/or traffic-related laboratory tests.

By its complexity an evaluation of driving ability can be compared to an evaluation of working capacity where often a multidisciplinary team is needed. When evaluating driving ability we have to take a step from low-level motor operations towards high-level mental actions, from the measurement of acuity of eyesight towards the testing of the flexibility of perception, from the diagnosis-based evaluation to the patient-based evaluation, from using the common pencil-paper tests towards the traffic-related task-specific tests and from the testing of separate single general non-driving-related factors towards an evaluation of the theoretically based driving performance as whole.

There is a pressing need to evaluate driving ability without an actual driving test but no reliable, standardised procedure is available. This study investigated the resulting distortion performance evaluation for different driver groups in on-road tests due to driving skills and driving style. Two groups, 15 female driving school students and 25 experienced male drivers were examined using cognitive and psychomotor tests and standard personality questionnaires as well as an on-road driving test. The students made significantly fewer errors on the driving test than the experienced drivers. The former group's driving performance could be predicted by errors on the laboratory tests, along with personality factors, while experienced drivers' driving errors were best predicted by slowness on laboratory tests. This study suggests that, when a series of standard cognitive and psychomotor tests are considered, different measures may apply in predicting young people's ability to drive safely based on assessing driving ability of experienced drivers, assumed lowered due to distorted driving style.